Structure, Process, and Outcome Quality of Surgical Site Infection Surveillance in Switzerland

OBJECTIVE

To assess the structure and quality of surveillance activities and to validate outcome detection in the Swiss national surgical site infection (SSI) surveillance program.

DESIGN

Countrywide survey of SSI surveillance quality.

SETTING

147 hospitals or hospital units with surgical activities in Switzerland.

METHODS

Site visits were conducted with on-site structured interviews and review of a random sample of 15 patient records per hospital: 10 from the entire data set and 5 from a subset of patients with originally reported infection. Process and structure were rated in 9 domains with a weighted overall validation score, and sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the identification of SSI.

RESULTS

Of 50 possible points, the median validation score was 35.5 (range, 16.25–48.5). Public hospitals (P<.001), hospitals in the Italian-speaking region of Switzerland (P=.021), and hospitals with longer participation in the surveillance (P=.018) had higher scores than others. Domains that contributed most to lower scores were quality of chart review and quality of data extraction. Of 49 infections, 15 (30.6%) had been overlooked in a random sample of 1,110 patient records, accounting for a sensitivity of 69.4% (95% confidence interval [CI], 54.6%–81.7%), a specificity of 99.9% (95% CI, 99.5%–100%), a positive predictive value of 97.1% (95% CI, 85.1%–99.9%), and a negative predictive value of 98.6% (95% CI, 97.7%–99.2%).

CONCLUSIONS

Irrespective of a well-defined surveillance methodology, there is a wide variation of SSI surveillance quality. The quality of chart review and the accuracy of data collection are the main areas for improvement.

Infect Control Hosp Epidemiol 2017;38:1172–1181

Sensitivity and specificity of the method used for ascertainment of healthcare-associated infections in the second Slovenian national prevalence survey

Introduction

The second Slovenian national healthcare-associated infections (HAIs) prevalence survey (SNHPS) was conducted in acute-care hospitals in 2011. The objective was to assess the sensitivity and specificity of the method used for the ascertainment of six types of HAIs (bloodstream infections, catheter-associated infections, lower respiratory tract infections, pneumoniae, surgical site infections, and urinary tract infections) in the University Medical Centre Ljubljana (UMCL).

Methods

A cross-sectional study was conducted in patients surveyed in the SNHPS in the UMCL using a retrospective medical chart review (RMCR) and European HAIs surveillance definitions. Sensitivity and specificity of the method used in the SNHPS using RMCR as a reference was computed for ascertainment of patients with any of the six selected types of HAIs and for individual types of HAIs. Agreement between the SNHPS and RMCR results was analyzed using Cohen’s kappa coefficient.

Results

1474 of 1742 (84.6%) patients surveyed in the SNHPS were included in RMCR. The sensitivity of the SNHPS method for detecting any of six HAIs was 90% (95% confidence interval (CI): 81%-95%) and specificity 99% (95% CI: 98%-99%). The sensitivity by type of HAI ranged from 63% (lower respiratory tract infections) to 92% (bloodstream infections). Specificity was at least 99% for all types of HAIs. Agreement between the two data collection approaches for HAIs overall was very good (κ=0.83).

Conclusions

The overall sensitivity of SNHPS collection method for ascertaining HAIs overall was high and the specificity was very high. This suggests that the estimated prevalence of HAIs in the SNHPS was credible.

Administrative Data Fail to Accurately Identify Cases of Healthcare-Associated Infection

Objective.

Some policy makers have embraced public reporting of healthcare-associated infections (HAIs) as a strategy for improving patient safety and reducing healthcare costs. We compared the accuracy of 2 methods of identifying cases of HAI: review of administrative data and targeted active surveillance.

Design, Setting, and Participants.

A cross-sectional prospective study was performed during a 9-month period in 2004 at the Children's Hospital of Philadelphia, a 418-bed academic pediatric hospital. “True HAI” cases were defined as those that met the definitions of the National Nosocomial Infections Surveillance System and that were detected by a trained infection control professional on review of the medical record. We examined the sensitivity and the positive and negative predictive values of identifying HAI cases by review of administrative data and by targeted active surveillance.

Results.

We found similar sensitivities for identification of HAI cases by review of administrative data (61%) and by targeted active surveillance (76%). However, the positive predictive value of identifying HAI cases by review of administrative data was poor (20%), whereas that of targeted active surveillance was 100%.

Conclusions.

The positive predictive value of identifying HAI cases by targeted active surveillance is very high. Additional investigation is needed to define the optimal detection method for institutions that provide HAI data for comparative analysis.

Using surveillance data to reduce healthcare-associated infection: a qualitative study in Sweden

INTRODUCTION

Healthcare-associated infection (HAI) surveillance data can be used to estimate the scope, spread and location of infections, monitor trends, evaluate preventive efforts, and improve practices, policy and facility planning. In Sweden, national point prevalence surveys (PPS) have been conducted twice yearly in all county councils since 2008.

AIM

The aim of this study was to identify key obstacles concerning the HAI surveillance process.

METHODS

Twenty-two infection control practitioners (ICPs) from all county councils in Sweden were interviewed, using semi-structured interview guides. Data were analysed using qualitative content analysis.

RESULTS

Sixteen types of obstacles pertaining to four surveillance stages were identified. Most obstacles were associated with the first two stages, which meant that the latter stages of this process, i.e. the use of the results to reduce HAI, were underdeveloped. The ICPs observed scepticism towards both the PPS methodology itself and the quality of the HAI data collected in the PPS, which hinders HAI surveillance realising its full potential in Swedish healthcare.

Challenges in reporting surgical site infections to the national surgical site infection surveillance and suggestions for improvement

INTRODUCTION

Mandatory orthopaedic surgical site infection (SSI) data in England are used as a benchmark to compare infection rates between participating hospitals. According to the national guidelines, trusts are required to submit their data for at least one quarter of the year but they are free to report for all quarters. Owing to this ambiguity, there is a concern about robust reporting across trusts and therefore the accuracy of these data. There is also concern about the accuracy of collection methods. The aim of this five-year retrospective study was to assess the accuracy of SSI reporting at two hospitals in South East England under the same trust.

METHODS

A retrospective review was carried out of five years of electronic medical records, microbiology data and readmission data of all patients who underwent hip and knee replacement surgery at these hospitals. These data were validated with the data submitted to Public Health England (PHE) and any discrepancy between the two was noted.

RESULTS

A significant difference was found in the SSI rates reported by the surveillance staff and our retrospective method.

CONCLUSIONS

Our study confirms the findings of a national survey, which raised concerns about the quality of SSI reporting and the usefulness of PHE SSI data for benchmarking purposes. To our knowledge, there are no previously published studies that have looked at the accuracy of the English orthopaedic SSI surveillance. In the light of our findings, there is an urgent need for external validation studies to identify the extent of the problem in the surveillance scheme. The governing bodies should also issue clear guidelines for reporting SSIs to maintain homogeneity and to present the true incidence of SSI. We suggest some measures that we have instituted to address these inadequacies that have led to significant improvements in reporting at our trust.

A pilot validation in 10 European Union Member States of a point prevalence survey of healthcare-associated infections and antimicrobial use in acute hospitals in Europe, 2011

Binary file ES_Abstracts_Final_ECDC.txt matches

Validation of Coronary Artery Bypass Graft Surgical Site Infection Surveillance Data From a Statewide Surveillance System in Australia

Objective.

To measure the accuracy and determine the positive predictive value (PPV) and negative predictive value (NPV) of data submitted to a statewide surveillance system for identifying surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery.

Design.

Retrospective review of hospital medical records comparing SSI data with surveillance data submitted by infection control consultants (ICCs).

Setting.

Victorian Hospital Acquired Infection Surveillance System (VICNISS) Coordinating Centre in Victoria, Australia.

Patients.

All patients reported to have an SSI following CABG surgery and a random sample of approximately 10% of patients reported not to have an SSI following CABG surgery.

Results.

The VICNISS ascertainment rate for CABG procedures in Victoria was 95%. One hundred sixty-nine medical records were reviewed, and reviewers agreed with ICCs about 46 (96%) of the patients reported as infected by the ICCs and 31 (91%) of the patients identified with a sternal SSI by the ICCs. In one-third of SSIs, the depth of SSI documented by ICCs was discordant with that documented by the reviewers. Disagreement about patients with donor site SSI was frequent. When the review findings were used as the reference standard, the PPV for ICC-reported SSI was 96% (95% confidence interval [CI], 86%-99%), and the NPV was 97% (95% CI, 92%-99%). For ICC-reported sternal SSI, the PPV was 91% (95% CI, 76%-98%) and the NPV was 98% (95% CI, 94%-100%).

Conclusions.

There was broad agreement on the number of infected patients and the number of patients with sternal SSI. However, discordance was frequent with respect to the depth of sternal SSI and the identification of donor site SSI. We recommend modifications to the methodology for National Noscomial Infection Surveillance System-based surveillance for SSI following CABG surgery.

Validation of Surgical Site Infection Surveillance in The Netherlands

Objectives.

To describe how continuous validation of data on surgical site infection (SSI) is being performed in the Dutch National Nosocomial Infection Surveillance System (Preventie Ziekenhuisinfecties door Surveillance [PREZIES]), to assess the quality and accuracy of the PREZIES data, and to present the corresponding outcomes of the assessment.

Design.

Mandatory, 1-day on-site validation visit to participating hospitals every 3 years. The process of surveillance, including the quality of the method of data collection, is validated by means of a structured interview. The use of SSI criteria is validated by review of medical records, with the judgment of the validation team as the criterion standard.

Setting.

Hospitals participating in PREZIES.

Results.

During 1999-2004, the validation team visited 40 hospitals and reviewed 859 medical charts. There was no deviation between reports of SSI by infection control professionals and findings by the PREZIES validation team at 30 hospitals and 1 deviation in each of 10 hospitals; the positive predictive value was 0.97, and the negative predictive value was 0.99. The validation team often gave advice to the hospital, aimed at perfecting the process of surveillance. On 2 occasions, data were removed from the PREZIES database after the validation visit revealed deviations from the SSI surveillance protocol that could have resulted in nonrepresentative SSI rate data.

Conclusions.

PREZIES is confident that the assembled Dutch SSI surveillance data are reliable and robust and are sufficiently accurate to be used as a reference for interhospital comparison. PREZIES will continue performing on-site validation visits, to improve the process of surveillance and ensure the reliability of the surveillance data.

Data use and effectiveness in electronic surveillance of healthcare associated infections in the 21st century: a systematic review

OBJECTIVE

As more electronic health records have become available during the last decade, we aimed to uncover recent trends in use of electronically available patient data by electronic surveillance systems for healthcare associated infections (HAIs) and identify consequences for system effectiveness.

METHODS

A systematic review of published literature evaluating electronic HAI surveillance systems was performed. The PubMed service was used to retrieve publications between January 2001 and December 2011. Studies were included in the review if they accurately described what electronic data were used and if system effectiveness was evaluated using sensitivity, specificity, positive predictive value, or negative predictive value. Trends were identified by analyzing changes in the number and types of electronic data sources used.

RESULTS

26 publications comprising discussions on 27 electronic systems met the eligibility criteria. Trend analysis showed that systems use an increasing number of data sources which are either medico-administrative or clinical and laboratory-based data. Trends on the use of individual types of electronic data confirmed the paramount role of microbiology data in HAI detection, but also showed increased use of biochemistry and pharmacy data, and the limited adoption of clinical data and physician narratives. System effectiveness assessments indicate that the use of heterogeneous data sources results in higher system sensitivity at the expense of specificity.

CONCLUSIONS

Driven by the increased availability of electronic patient data, electronic HAI surveillance systems use more data, making systems more sensitive yet less specific, but also allow systems to be tailored to the needs of healthcare institutes' surveillance programs.

Quality control of the surveillance programme of ICU-acquired infection (ENVIN-HELICS registry) in Spain

BACKGROUND

Data validation is an essential aspect for the accuracy of a nosocomial infection surveillance registry.

AIM

To report the results of the first quality control programme in the national surveillance programme of intensive care unit (ICU)-acquired infection in Spain (ENVIN-HELICS registry).

METHOD

During 2008, of 13,824 records included in the database, 1500 (10.8%) registries from 20 ICUs were reviewed. These ICUs were selected at random and stratified according to the number of cases included in the registry. The proportion of infected patients, which was 9.6% [95% confidence interval (CI) 8.09-11.16], was maintained during the selection of cases for review. Two physicians were trained for the purpose of the study and undertook the review.

RESULTS

Overall sensitivity, specificity and positive and negative predictive values of the ENVIN-HELICS registry for the identification of patients with any device-related infection acquired during their ICU stay were 86.0% (95% CI 80.0-92.0), 98.7% (95% CI 82.19-93.6), 87.9% (95% CI 82.19-93.6) and 98.5% (95% CI 97.8-99.2), respectively, with a kappa index of 0.85 (95% CI 0.79-0.92). Secondary bloodstream infection had the lowest sensitivity (59.3%), and intubation-associated pneumonia had the highest sensitivity (86.3%).

CONCLUSION

There was good correlation between data reported by the registrars and data validated by auditors, confirming the reliability of the ENVIN-HELICS registry.

Automated detection of healthcare associated infections: external validation and updating of a model for surveillance of drain-related meningitis

OBJECTIVE

Automated surveillance of healthcare-associated infections can improve efficiency and reliability of surveillance. The aim was to validate and update a previously developed multivariable prediction model for the detection of drain-related meningitis (DRM).

DESIGN

Retrospective cohort study using traditional surveillance by infection control professionals as reference standard.

PATIENTS

Patients receiving an external cerebrospinal fluid drain, either ventricular (EVD) or lumbar (ELD) in a tertiary medical care center. Children, patients with simultaneous drains, <1 day of follow-up or pre-existing meningitis were excluded leaving 105 patients in validation set (2010-2011) and 653 in updating set (2004-2011).

METHODS

For validation, the original model was applied. Discrimination, classification and calibration were assessed. For updating, data from all available years was used to optimally re-estimate coefficients and determine whether extension with new predictors is necessary. The updated model was validated and adjusted for optimism (overfitting) using bootstrapping techniques.

RESULTS

In model validation, the rate of DRM was 17.4/1000 days at risk. All cases were detected by the model. The area under the ROC curve was 0.951. The positive predictive value was 58.8% (95% CI 40.7-75.4) and calibration was good. The revised model also includes Gram stain results. Area under the ROC curve after correction for optimism was 0.963 (95% CI 0.953- 0.974). Group-level prediction was adequate.

CONCLUSIONS

The previously developed multivariable prediction model maintains discriminatory power and calibration in an independent patient population. The updated model incorporates all available data and performs well, also after elaborate adjustment for optimism.

Evaluation of the national surveillance system for point-prevalence of healthcare-associated infections in hospitals and in long-term care facilities for elderly in Norway, 2002-2008

Background

Since 2002, the Norwegian Institute of Public Health has invited all hospitals and long-term care facilities for elderly (LTCFs) to participate in two annual point-prevalence surveys covering the most frequent types of healthcare-associated infections (HAIs). In a comprehensive evaluation we assessed how well the system operates to meet its objectives.

Methods

Surveillance protocols and the national database were reviewed. Data managers at national level, infection control practitioners and ward personnel in hospitals as well as contact persons in LTCFs involved in prevalence data collection were surveyed.

Results

The evaluation showed that the system was structurally simple, flexible and accepted by the key partners. On average 87% of hospitals and 32% of LTCFs participated in 2004-2008; high level of data completeness was achieved. The data collected described trends in the prevalence of reportable HAIs in Norway and informed policy makers. Local results were used in hospitals to implement targeted infection control measures and to argue for more resources to a greater extent than in LTCFs. Both the use of simplified Centers for Disease Control and Prevention (CDC) definitions and validity of data seemed problematic as compliance with the standard methodology were reportedly low.

Conclusions

The surveillance system provides important information on selected HAIs in Norway. The system is overall functional and well-established in hospitals, however, requires active promotion in LTCFs. Validity of data needs to be controlled in the participating institutions before reporting to the national level.

Automated detection of external ventricular and lumbar drain-related meningitis using laboratory and microbiology results and medication data

Objective

Monitoring of healthcare-associated infection rates is important for infection control and hospital benchmarking. However, manual surveillance is time-consuming and susceptible to error. The aim was, therefore, to develop a prediction model to retrospectively detect drain-related meningitis (DRM), a frequently occurring nosocomial infection, using routinely collected data from a clinical data warehouse.

Methods

As part of the hospital infection control program, all patients receiving an external ventricular (EVD) or lumbar drain (ELD) (2004 to 2009; n = 742) had been evaluated for the development of DRM through chart review and standardized diagnostic criteria by infection control staff; this was the reference standard. Children, patients dying <24 hours after drain insertion or with <1 day follow-up and patients with infection at the time of insertion or multiple simultaneous drains were excluded. Logistic regression was used to develop a model predicting the occurrence of DRM. Missing data were imputed using multiple imputation. Bootstrapping was applied to increase generalizability.

Results

537 patients remained after application of exclusion criteria, of which 82 developed DRM (13.5/1000 days at risk). The automated model to detect DRM included the number of drains placed, drain type, blood leukocyte count, C-reactive protein, cerebrospinal fluid leukocyte count and culture result, number of antibiotics started during admission, and empiric antibiotic therapy. Discriminatory power of this model was excellent (area under the ROC curve 0.97). The model achieved 98.8% sensitivity (95% CI 88.0% to 99.9%) and specificity of 87.9% (84.6% to 90.8%). Positive and negative predictive values were 56.9% (50.8% to 67.9%) and 99.9% (98.6% to 99.9%), respectively. Predicted yearly infection rates concurred with observed infection rates.

Conclusion

A prediction model based on multi-source data stored in a clinical data warehouse could accurately quantify rates of DRM. Automated detection using this statistical approach is feasible and could be applied to other nosocomial infections.

Quality of data reported to a smaller-hospital pilot surveillance program

This data quality study assessed the accuracy of data collected as part of a pilot smaller-hospital surveillance program for methicillin-resistant Staphylococcus aureus (MRSA) infection and bloodstream infection (BSI). For reported MRSA infection, estimated values were as follows: sensitivity, 40%; specificity, 99.9%; and positive predictive value, 33.3%. For reported BSI, estimated values were as follows: sensitivity, 42.9%; specificity, 99.8%; and positive predictive value, 37.5%.

Prevalence of hospital infection and antibiotic use at a university medical center in Hong Kong

Hospital infection prevalence surveys were performed in our 1400-bed University medical centre in Hong Kong from 1985 to 1988. We investigated the rates of four major hospital-acquired infections (HAIs) (pneumonia, symptomatic urinary tract infection, surgical site infection and laboratory-confirmed bloodstream infection) in order to identify current distribution and any changes after 15 years. A one-day point prevalence study was performed on 7 September 2005. All inpatients were surveyed for HAIs, community-acquired infections (CAIs), risk factors, pathogenic isolates and antibiotics prescribed. Infections were diagnosed according to Centers for Disease Control and Prevention (CDC) criteria. In total, 1021 patients were surveyed; of these, 41 had 42 HAIs (4% prevalence) and 389 (38%) were receiving antibiotics. The commonest HAI was pneumonia (1.4%) followed by bloodstream infection (0.9%) and symptomatic urinary tract infection (0.8%). The prevalence of postoperative surgical site infection was 5.6%. The nosocomial prevalence rate was highest in the Intensive Care Unit, followed by the Pediatric and Neonatal Intensive Care Units, Children's Cancer Centre/Bone Marrow Transplant Unit and Orthopaedics with Traumatology. Meticillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa were the commonest pathogens. The rates are significantly lower than previously and reflect the increased resources for infection control made available following the outbreak of severe acute respiratory syndrome (SARS).

Reliability of case definitions for public health surveillance assessed by Round-Robin test methodology

BACKGROUND

Case definitions have been recognized to be important elements of public health surveillance systems. They are to assure comparability and consistency of surveillance data and have crucial impact on the sensitivity and the positive predictive value of a surveillance system. The reliability of case definitions has rarely been investigated systematically.

METHODS

We conducted a Round-Robin test by asking all 425 local health departments (LHD) and the 16 state health departments (SHD) in Germany to classify a selection of 68 case examples using case definitions. By multivariate analysis we investigated factors linked to classification agreement with a gold standard, which was defined by an expert panel.

RESULTS

A total of 7870 classifications were done by 396 LHD (93%) and all SHD. Reporting sensitivity was 90.0%, positive predictive value 76.6%. Polio case examples had the lowest reporting precision, salmonellosis case examples the highest (OR = 0.008; CI: 0.005-0.013). Case definitions with a check-list format of clinical criteria resulted in higher reporting precision than case definitions with a narrative description (OR = 3.08; CI: 2.47-3.83). Reporting precision was higher among SHD compared to LHD (OR = 1.52; CI: 1.14-2.02).

CONCLUSION

Our findings led to a systematic revision of the German case definitions and build the basis for general recommendations for the creation of case definitions. These include, among others, that testable yes/no criteria in a check-list format is likely to improve reliability, and that software used for data transmission should be designed in strict accordance with the case definitions. The findings of this study are largely applicable to case definitions in many other countries or international networks as they share the same structural and editorial characteristics of the case definitions evaluated in this study before their revision.

A quality management project in 8 selected hospitals to reduce nosocomial infections: a prospective, controlled study

OBJECTIVE

To reduce the number of nosocomial infections (NIs) in surgical patients by a quality management approach.

DESIGN

Prospective, controlled study in 8 medium-sized hospitals during a 26-month period.

SETTING

Four study hospitals and 4 control hospitals.

METHODS

In two 10-month intervention periods, 4 external physicians introduced quality circles and ongoing surveillance in the 4 study hospitals. There were three 8-week observation periods in all 8 hospitals with the same physicians before, during, and after the intervention periods.

RESULTS

During the first observation period, almost identical overall incidence densities were found for the study hospitals and the control hospitals. During the course of the study, the overall incidence density decreased significantly in the study hospitals (risk ratio [RR], 0.74; 95% confidence interval [CI 95], 0.59 to 0.94) and nonsignificantly in the control hospitals (RR, 0.90; CI 95 0.70 to 1.16). With the use of a Cox regression model to evaluate the impact of the intervention periods while taking into account the distribution of risk factors for NI in both groups, a significant risk reduction (RR, 0.75; CI 95, 0.58 to 0.97) was observed after the first intervention period when comparing study and control hospitals. At the end of the study (ie, after the second intervention period), the difference between the study hospitals and the control hospitals was not significant (RR, 0.78; CI 95, 0.60 to 1.01). This was due to no further improvement at the end of the study in the study hospitals and a decrease in the control hospitals.

CONCLUSION

This study demonstrates that NI rates can be significantly reduced by appropriate intervention methods in hospitals that are interested in quality management activities. However, continuous intense efforts are necessary to maintain these improvements.

Sixteen years' surveillance of surgical sites in an Irish acute-care hospital

OBJECTIVE

To report a program of continuous surveillance of surgical-site infections (SSIs) using basic surveillance methods.

DESIGN

Analysis of routine prospective surveillance data.

SETTING

Two hospitals in Ireland (300 and 350 beds) that merged and moved to a new 650-bed hospital in 1987.

PATIENTS

59,335 surgical sites of postoperative patients.

INTERVENTIONS

Surgical sites were surveyed by one infection control nurse and SSI rates were produced for selected operations and surgical services. The program was conducted in general accordance with the 1999 HICPAC guidelines, but differed in surveillance strategy. Operations were limited to two to three risk classifications, assigned by the infection control nurse.

RESULTS

The overall SSI rate was 4.5%, with 2.4% in clean surgery. Apart from increases in the 3rd, 4th, 13th, and 14th years, rates remained relatively stable during the 16 years. Few significant decreases in SSI rates in surgical services or specific operations were shown, apart from the following: vascular surgery, 8.1% to 5% between the first 8 years and the last 8 years; general surgery services, 9% to 5%, and gynecology, 15.8% to 1.7%, both in the first year compared with in subsequent years; and gastric operations, 21% to 4.3% between the first year and the second year. Organ/space infection was identified in 0.5% of 17,804 operations, including 0.4% meningitis after neurosurgical procedures, 3% graft infections after vascular bypass operations, and 0.2% intra-abdominal infections after abdominal surgery.

CONCLUSIONS

With the use of basic principles of surveillance and modest resources, procedure-specific SSI rates were produced, with little significant change during the 16 years. Despite limitations in case-finding, risk stratification, feedback, and surveillance methods, the overall SSI rates were comparable with other published data.

Converting incidence and prevalence data of nosocomial infections: results from eight hospitals

OBJECTIVE

To investigate the use of the formula of Rhame and Sudderth for the interconversion of prevalence and incidence data on the frequency of nosocomial infections.

DESIGN

Comparison of observed and calculated incidence data and prevalence data.

SETTING

One 8-week incidence investigation in the surgical and intensive care units of eight medium-sized hospitals; three separate point-prevalence studies in the same units.

RESULTS

The overall prevalence observed after the three prevalence studies in 2,169 patients was 6.8% (95% confidence interval [CI95], 5.7-8.0). In 2,882 discharged patients observed during the incidence study, the mean hospitalization was 9.8 days; patients with one or more nosocomial infection had a mean hospitalization time of 22.3 days and a mean interval of 8.2 days from admission to the first day of infection. Based on these data, the overall calculated incidence was 4.7%, whereas the observed incidence was 4.3% (CI95, 3.6-5.2). Vice versa, an overall prevalence of 6.2% was found when calculated from the observed incidence data. The incidence data calculated from prevalence data also were within the confidence interval of the incidences observed for urinary tract infections and surgical-site infections. (However, it was not possible to convert the data for two of the eight hospitals.)

CONCLUSION

The approximate mathematical relationship between the prevalence and incidence data of nosocomial infection is confirmed by this study. However, although it is theoretically possible, we would not recommend the conversion of prevalence into incidence data or vice versa.

How many nosocomial infections are missed if identification is restricted to patients with either microbiology reports or antibiotic administration?

OBJECTIVE

To investigate how many nosocomial infections would be missed if surveillance activities were restricted to patients having either microbiology reports or antibiotic administration.

DESIGN

Analysis of data from a large prevalence study on nosocomial infections (Nosocomial Infections in Germany-Surveillance and Prevention).

SETTING

A total of 14,966 patients were investigated in medical, surgical, obstetric-gynecologic, and intensive-care units of 72 German hospitals representatively selected according to size. Five hundred eighteen patients (3.5%) had at least one nosocomial infection. Microbiology reports were available for 56.6% of these patients on the prevalence day, and 86.3% received antibiotics.

RESULTS

Only 31 nosocomially infected patients (6%) would have been missed by using either microbiology reports or antibiotic treatment as an indicator. These indicators of nosocomial infections had a high diagnostic sensitivity for nosocomial pneumonia (98.8%), urinary tract infections (96.3%), and primary bloodstream infections (95.3%), but a lower sensitivity for wound infections (85.4%). Thus, 97.4% of all nosocomial infections were found with this method in intensive-care units and 96.1% in medicine units, but only 89.7% in surgical departments. In 9 (12.5%) of 72 hospitals, the overall sensitivity would have been <80% using a combination of the two indicators. For this reason, the situation in one's own hospital should be checked before using this method.

CONCLUSIONS

After checking the situation in one's own hospital, the "either-or" approach using the two indicators "microbiology report" and "antibiotic administration" can be recommended as a time-saving measure to diagnose pneumonia, urinary tract, and primary bloodstream infections. For wound infections, additional information obtained by changing dressings or participating in ward rounds is necessary to achieve satisfactory sensitivity in the surveillance of nosocomial infections. Of course, it is necessary that the surveillance staff discard all false positives to ensure a satisfactory specificity.

Prevalence and risk factors for nosocomial lower respiratory tract infections in German hospitals

The prevalence and risk factors for nosocomial lower respiratory tract infections (LRTI) in Germany were determined as part of a national survey on nosocomial infections. The study included 14,966 patients in 72 representatively selected hospitals with departments of general medicine, surgery, obstetrics, gynecology, and intensive care units (ICU). Surveillance was carried out by four previously validated medical doctors who strictly applied the CDC-criteria for diagnosis of nosocomial infections. The overall prevalence of hospital-acquired LRTI was 0.72% with the highest rate in hospitals with more than 600 beds (1.08%) and among the patients on intensive care units (9.00%). Ventilator-associated pneumonia rates were highest in patients on ICUs (13.27). Polytrauma, impaired consciousness, chronic airway disease, prior surgery, and cardiovascular disease were significantly related to the occurrence of nosocomial LRTI. P. aeruginosa was the predominant organism causing nosocomial LRTI. Nosocomial LRTI remain a problem mainly on ICUs. Patients at risk should be monitored with extra care.